/* * nmi.c - Safe printk in NMI context * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, see . */ #include #include #include #include #include #include #include #include "internal.h" /* * printk() could not take logbuf_lock in NMI context. Instead, * it uses an alternative implementation that temporary stores * the strings into a per-CPU buffer. The content of the buffer * is later flushed into the main ring buffer via IRQ work. * * The alternative implementation is chosen transparently * via @printk_func per-CPU variable. * * The implementation allows to flush the strings also from another CPU. * There are situations when we want to make sure that all buffers * were handled or when IRQs are blocked. */ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default; static int printk_nmi_irq_ready; atomic_t nmi_message_lost; #define NMI_LOG_BUF_LEN ((1 << CONFIG_NMI_LOG_BUF_SHIFT) - \ sizeof(atomic_t) - sizeof(struct irq_work)) struct nmi_seq_buf { atomic_t len; /* length of written data */ struct irq_work work; /* IRQ work that flushes the buffer */ unsigned char buffer[NMI_LOG_BUF_LEN]; }; static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq); /* * Safe printk() for NMI context. It uses a per-CPU buffer to * store the message. NMIs are not nested, so there is always only * one writer running. But the buffer might get flushed from another * CPU, so we need to be careful. */ static int vprintk_nmi(const char *fmt, va_list args) { struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq); int add = 0; size_t len; again: len = atomic_read(&s->len); /* The trailing '\0' is not counted into len. */ if (len >= sizeof(s->buffer) - 1) { atomic_inc(&nmi_message_lost); return 0; } /* * Make sure that all old data have been read before the buffer was * reseted. This is not needed when we just append data. */ if (!len) smp_rmb(); add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args); /* * Do it once again if the buffer has been flushed in the meantime. * Note that atomic_cmpxchg() is an implicit memory barrier that * makes sure that the data were written before updating s->len. */ if (atomic_cmpxchg(&s->len, len, len + add) != len) goto again; /* Get flushed in a more safe context. */ if (add && printk_nmi_irq_ready) { /* Make sure that IRQ work is really initialized. */ smp_rmb(); irq_work_queue(&s->work); } return add; } static void printk_nmi_flush_line(const char *text, int len) { /* * The buffers are flushed in NMI only on panic. The messages must * go only into the ring buffer at this stage. Consoles will get * explicitly called later when a crashdump is not generated. */ if (in_nmi()) printk_deferred("%.*s", len, text); else printk("%.*s", len, text); } /* printk part of the temporary buffer line by line */ static int printk_nmi_flush_buffer(const char *start, size_t len) { const char *c, *end; bool header; c = start; end = start + len; header = true; /* Print line by line. */ while (c < end) { if (*c == '\n') { printk_nmi_flush_line(start, c - start + 1); start = ++c; header = true; continue; } /* Handle continuous lines or missing new line. */ if ((c + 1 < end) && printk_get_level(c)) { if (header) { c = printk_skip_level(c); continue; } printk_nmi_flush_line(start, c - start); start = c++; header = true; continue; } header = false; c++; } /* Check if there was a partial line. Ignore pure header. */ if (start < end && !header) { static const char newline[] = KERN_CONT "\n"; printk_nmi_flush_line(start, end - start); printk_nmi_flush_line(newline, strlen(newline)); } return len; } /* * Flush data from the associated per_CPU buffer. The function * can be called either via IRQ work or independently. */ static void __printk_nmi_flush(struct irq_work *work) { static raw_spinlock_t read_lock = __RAW_SPIN_LOCK_INITIALIZER(read_lock); struct nmi_seq_buf *s = container_of(work, struct nmi_seq_buf, work); unsigned long flags; size_t len; int i; /* * The lock has two functions. First, one reader has to flush all * available message to make the lockless synchronization with * writers easier. Second, we do not want to mix messages from * different CPUs. This is especially important when printing * a backtrace. */ raw_spin_lock_irqsave(&read_lock, flags); i = 0; more: len = atomic_read(&s->len); /* * This is just a paranoid check that nobody has manipulated * the buffer an unexpected way. If we printed something then * @len must only increase. Also it should never overflow the * buffer size. */ if ((i && i >= len) || len > sizeof(s->buffer)) { const char *msg = "printk_nmi_flush: internal error\n"; printk_nmi_flush_line(msg, strlen(msg)); len = 0; } if (!len) goto out; /* Someone else has already flushed the buffer. */ /* Make sure that data has been written up to the @len */ smp_rmb(); i += printk_nmi_flush_buffer(s->buffer + i, len - i); /* * Check that nothing has got added in the meantime and truncate * the buffer. Note that atomic_cmpxchg() is an implicit memory * barrier that makes sure that the data were copied before * updating s->len. */ if (atomic_cmpxchg(&s->len, len, 0) != len) goto more; out: raw_spin_unlock_irqrestore(&read_lock, flags); } /** * printk_nmi_flush - flush all per-cpu nmi buffers. * * The buffers are flushed automatically via IRQ work. This function * is useful only when someone wants to be sure that all buffers have * been flushed at some point. */ void printk_nmi_flush(void) { int cpu; for_each_possible_cpu(cpu) __printk_nmi_flush(&per_cpu(nmi_print_seq, cpu).work); } /** * printk_nmi_flush_on_panic - flush all per-cpu nmi buffers when the system * goes down. * * Similar to printk_nmi_flush() but it can be called even in NMI context when * the system goes down. It does the best effort to get NMI messages into * the main ring buffer. * * Note that it could try harder when there is only one CPU online. */ void printk_nmi_flush_on_panic(void) { /* * Make sure that we could access the main ring buffer. * Do not risk a double release when more CPUs are up. */ if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) { if (num_online_cpus() > 1) return; debug_locks_off(); raw_spin_lock_init(&logbuf_lock); } printk_nmi_flush(); } void __init printk_nmi_init(void) { int cpu; for_each_possible_cpu(cpu) { struct nmi_seq_buf *s = &per_cpu(nmi_print_seq, cpu); init_irq_work(&s->work, __printk_nmi_flush); } /* Make sure that IRQ works are initialized before enabling. */ smp_wmb(); printk_nmi_irq_ready = 1; /* Flush pending messages that did not have scheduled IRQ works. */ printk_nmi_flush(); } void printk_nmi_enter(void) { this_cpu_write(printk_func, vprintk_nmi); } void printk_nmi_exit(void) { this_cpu_write(printk_func, vprintk_default); } SyS_ioctl+0x4e/0x80 entry_SYSCALL_64_fastpath+0x13/0x94 INFO: Freed in drm_event_cancel_free+0xa3/0xb0 [drm] age=0 cpu=3 pid=1529 __slab_free+0x48/0x2e0 kfree+0x159/0x1a0 drm_event_cancel_free+0xa3/0xb0 [drm] drm_mode_atomic_ioctl+0x86d/0xab0 [drm] drm_ioctl+0x2b3/0x490 [drm] do_vfs_ioctl+0x69c/0x700 SyS_ioctl+0x4e/0x80 entry_SYSCALL_64_fastpath+0x13/0x94 INFO: Slab 0xffffde1f0997b080 objects=17 used=2 fp=0xffff92fb65ec2578 flags=0x200000000008101 INFO: Object 0xffff92fb65ec2578 @offset=1400 fp=0xffff92fb65ec2ae8 Redzone ffff92fb65ec2570: bb bb bb bb bb bb bb bb ........ Object ffff92fb65ec2578: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec2588: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec2598: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec25a8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec25b8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec25c8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec25d8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff92fb65ec25e8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk. Redzone ffff92fb65ec25f8: bb bb bb bb bb bb bb bb ........ Padding ffff92fb65ec2738: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ CPU: 3 PID: 180 Comm: kworker/3:2 Tainted: G BU 4.10.0-rc6-patser+ #5039 Hardware name: /NUC5PPYB, BIOS PYBSWCEL.86A.0031.2015.0601.1712 06/01/2015 Workqueue: events intel_atomic_helper_free_state [i915] Call Trace: dump_stack+0x4d/0x6d print_trailer+0x20c/0x220 free_debug_processing+0x1c6/0x330 ? drm_atomic_state_default_clear+0xf7/0x1c0 [drm] __slab_free+0x48/0x2e0 ? drm_atomic_state_default_clear+0xf7/0x1c0 [drm] kfree+0x159/0x1a0 drm_atomic_state_default_clear+0xf7/0x1c0 [drm] ? drm_atomic_state_clear+0x30/0x30 [drm] intel_atomic_state_clear+0xd/0x20 [i915] drm_atomic_state_clear+0x1a/0x30 [drm] __drm_atomic_state_free+0x13/0x60 [drm] intel_atomic_helper_free_state+0x5d/0x70 [i915] process_one_work+0x260/0x4a0 worker_thread+0x2d1/0x4f0 kthread+0x127/0x130 ? process_one_work+0x4a0/0x4a0 ? kthread_stop+0x120/0x120 ret_from_fork+0x29/0x40 FIX kmalloc-128: Object at 0xffff92fb65ec2578 not freed Fixes: 3b24f7d67581 ("drm/atomic: Add struct drm_crtc_commit to track async updates") Fixes: 9626014258a5 ("drm/fence: add in-fences support") Cc: <stable@vger.kernel.org> # v4.8+ Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1485854725-27640-1-git-send-email-maarten.lankhorst@linux.intel.com
Diffstat (limited to 'include/uapi/asm-generic/poll.h')